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Questions and Answers
The largest part of the middle and incisal portions of the lingual area is ______.
concave
Mesial and distal marginal ridges border the ______, the lingual portion of the incisal aspect.
concavity
The second form is relatively ______ at the cervix, where the root joins the crown.
narrow
Crown sizes are ______ dimorphic, with male larger than female.
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Gender specific correlations between enamel thickness and crown width of ______ are low.
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The crown of the maxillary central incisor will be ______ mm long from the highest point on the cervical line to the lowest point on the incisal edge.
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The mesiodistal measurement will be ______ mm wide at the contact areas.
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The mesiodistal measurement, where the root joins the crown, will be ______ mm less.
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The crests of curvature mesially and distally on the crown represent the areas at which the central incisor contacts its ______.
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The distal outline of the crown is more ______ than the mesial outline.
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The incisal outline tends to curve downward toward the center of the ______ outline.
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The cervical outline of the crown follows a ______ direction with the curvature rootwise.
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The root of the central incisor from the labial aspect is ______-shaped.
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A line drawn through the center of the root and crown of the maxillary central incisor tends to parallel the ______ outline of the crown and root.
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The root is usually ______ mm longer than the crown, although it varies considerably.
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Study Notes
Maxillary Central Incisor
- The lingual topography of the maxillary central incisor gives a scoop-like form to the crown.
- The maxillary central incisor is the widest mesiodistally of any of the anterior teeth.
- The labial face is less convex than that of the maxillary lateral incisor or canine, giving it a squared or rectangular appearance.
- The crown has a nearly straight incisal edge, a cervical line with even curvature toward the root, and a mesial side with a straight outline.
- The distal side is more curved, with a mesial incisal angle that is relatively sharp and a distal incisal angle that is rounded.
- The enamel surface is relatively smooth, with mamelons visible on the incisal ridge when the tooth is newly erupted or has little wear.
- Developmental lines on the labial surface divide the surface into three parts, most noticeable at the middle portion.
- Lingually, the surface form is more irregular, with a concave middle and incisal portion bordered by mesial and distal marginal ridges.
Variations
- Exaggeration of the marginal ridges, known as a shovel-shaped incisor, is a genetically determined variation seen in Mongoloid races, including North and South American Indians.
- Anomalies include a short root or an unusually long crown.
- There are two basic forms of the maxillary central incisor: one relatively wide at the cervix and the other relatively narrow at the cervix.
- Crown sizes are gender dimorphic, with male larger than female, although the extent of dimorphism varies among populations.
Labial Aspect of Maxillary Central Incisor
- The crown of the average central incisor is 10-11 mm long from the cervical line to the incisal edge.
- The mesiodistal measurement of the crown at the contact areas is 8-9 mm wide.
- The mesiodistal measurement at the root-crown junction is 1.5-2 mm less than at the contact areas.
- The crests of curvature mesially and distally on the crown represent the contact areas with neighboring teeth.
- The mesial outline of the crown is slightly convex, with the crest of curvature approaching the mesioincisal angle.
- The distal outline of the crown is more convex than the mesial outline, with the crest of curvature higher toward the cervical line.
- The distoincisal angle is not as sharp as the mesioincisal angle, with the extent of curvature dependent on the typal form of the tooth.
- The incisal outline is usually regular and straight in a mesiodistal direction after the tooth has been in function.
- The incisal outline tends to curve downward toward the center of the crown outline, making the crown length greater at the center than at the mesial angles.
- The cervical outline of the crown follows a semicircular direction, curving rootwise from the mesial to the distal root outline.
- The root of the central incisor is cone-shaped, usually with a relatively blunt apex, and has a regular outline mesially and distally.
- The root is usually 2 or 3 mm longer than the crown, although it varies considerably.
- A line drawn through the center of the root and crown tends to parallel the mesial outline of the crown and root.
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Description
Learn about the characteristics and variations of the maxillary central incisor, including its shape, marginal ridges, and root development. Understand the differences seen in Mongoloid races and other anomalies.
